Method and means for the take-off of aircraft



Dec. 4, 1951 J. A. TROENDLE METHOD AND MEANS FOR THE TAKEOFF OF AIRCRAFT Filed Sept. 19, 1947 '7 Sheets-Sheet 1 Dec. 4, 1951 J. A. TROENDLE METHOD AND MEANS FOR THE TAKEOFF 0F AIRCRAFT '7 Sheets-Sheet 2 Filed Sept. 19, 1947 n m a 0F GRAVITY Dec. 4, 1951 J. A. TRQENDLE METHOD AND MEANS FOR THE TAKEOFF OF AIRCRAFT 7 Sheets-Sheet 3 Filed Sept. 19, 1947 CENTER OF GRAVITY INVENTOR Dec. 4, 1951 I J. A. TROENDLE METHOD AND MEANS FOR THE TAKEOFF OF AIRCRAFT 7 Sheets-Sheet 4 Filed Sept. 19, 1947 2 f WW3 a R M 1 U a INVENTOR (764/? ,4. 7774E/VOZf Dec. 4, 1951 J. A. TROENDLE 2,577,335

METHOD AND MEANS FOR THE TAKEQFF 0F AIRCRAFT Filed Sept. 19, 1947 7 Sheets-Sheet 5 g Q 41 41' Y I I K 43 l 0.45 41 G 46 FILOZQQ P Dec. 4, 1951 J, A. TR OENDLE 2,577,385

METHOD AND MEANS FOR THE TAKEQFF OF AIRCRAFT Filed Sept. 19, 1947 V 7 Sheets-Sheet e AB BURN? Dec. 4, 1951 J. A. TROENDLE METHOD AND MEANS FOR THE TAKEOFF 0F AIRCRAFT Filed Sept. 19, 1947 '7 Sheets-Sheet 7 INVENTOR Jar/V 4. Mam 94f Dads rum Q1345 Patented Dec. 4, 1951 METHOD AND MEANS FORTHE'TAKE-OFF Q or AIRCRAFT :J,ean A.V. -'Ir0,end1, Geneva, Switzerland A nglicaflonsqptember 19, 1947-, SerialNo, 774;:929

"This invention relates to an improved method tor -take-off of'aircraft and meansfor carrying thesameinto'practice 'Alprimary object of the invention is to efiec't :af mterial" reduction of the-fair drag exerted on thelandinggear during take-off at a time where the demand for powerf rom the power plant is at itsvmaximumgthereby-resulting in either a shortening :of the minimum take-oif run with a prescribed; load; or an increase of *the loajd capaclty .for -a-g prescribed :lengjsh for the take-oil run;

Amore specific object residesin "the method and means 'for"retractinga;portion;of'the landing gear during take-off at-artime -wherethe;aircra'itiis still traveling ;o,n"the groundgwhereby an advantageous ;reducti on in; air drag is obtained. This objective may be carried-out with various mpesjof landing ear;

For example, in a retractable landing-gear of t eb cy tsi rit s, pos i le npr v e a' war wh el t ut a d a led ma n, s r n. t vertical axial ,planenoi the ship, themain .Strut b in moi/ably :mountedjto allow forward longitudinal" shiiting of ,the "wheel or wheels of the main strut from a normal-positionin baclg'oi thecentergof balance of-the aircraft'to. -an'advanced position justibelowsaid center of balance.

Also; by way of further example; the scope ofthe invention "includes-:2. retractable jlanding -gear offlihe tricycle type "which "comprises a wheeled front strutanda pair of wheeledmainstruts, the

"saidpainof main struts being movably mounted to allow longitudinal forward motion of their wheels-from anorrnal position "-in, back. of-the center of balance of' s aid aircraft to'an advanced position in+the-vertical transverse plane through said center of balance;

Moreover, the invention is also applicable and highlyusefulin connection with retractable. landtrollediby, a propriate. means ior r tra tin f a d Wheeled lorwa idlstrutand. the. back pa rof tmain wheeledxst tutsrwhileisaidmcentral pair,ot wheeled stzl tssstillisunpqrt.xtheiairorait Qnzits "takeoil.

willmorezr adflysaprear w ll-tatt e aboreandeth rnti ntsi-i ivi wtwliioh -.the natnremL-h "111i" ve tioniis, h.tterwndersto izthero sists:

.4 @Glaims. (Cl. 244-102) hereinafter more Tully described, illustrated and claimed.

"The drawingsdiagrammaticallyillustrate "by way of 'example,'*not by: way of limitation,:several forms oi embodiment ofithe invention.

Figure 1' is a s'ide -viewsof' an -aircraft illustrating the first-'form'tof:embodiment of'the invention;

1Q; the eembio ti nsand a ran ement, iQf ZBflfiSl v and including aianding gear of theibicycle'type, Figure 2 is :a front :VieW Of-the aircraftshown in Figure l.

Figure'B isarsideelevation'ofthe aircraftshown in-Eigure 1 in a"la-terstage' of the-take-oflr run.

Figure l is a:si'de' View ofzan airoraft illustrat v ing a second embodim'enti of the invention as. ap-.- plied to a landing gear of the tricycle 'type.

Figure 5 is=afr0nt view of -theaircraftsshownin Figure l.

Figure 6"is=--a side elevation of the aircraft shown in' Fi'gure-4' in asubsequent -'stage of-the take-ofi run;

Figure? is a -side elevation ofanaircraftiHustratinga fith-ird "form of the invention, namely 1 an embodiment 'including three main 's'trutscarrying the main-wheels and l a wheeledTront strut.

Figure 8 is :a front 1 elevation of" the :aircraft shown in Figure 'l'.

Figure Q is-a bottom plan of the aircra'ftshown in Figure l Fig'ures m and' l lare-sideelevations of the -aircraft shown in Figure 7 "in later *stages of the: take off run.

Figure =I2 is a side elevation of another :air-; craft within the scope "of the third "form of :the' invention, and including three main estruts car-- ty ng-the main- 'wh'ee1s,'- an'd with a wheeled front strut.

Figure is a front elevation of the aircraft shown in Figure 12;

Eigure '1 4';is a bottom splan view Ofthe: aircraft shown-inifiguream. V

Figures'I5 .and lfi are sideaelevations oftheaircrafitshown'in Figur-eilzinsuccessive laterstages oitthatake-lofiirun.

Figure 17 is a front elevation ofithe aircraft Figure ZO-is-aIbQttQm-Jplaniviewiof the aircrailt :Figures :21 and: 122;. $128. vside :elerationsmf: the aircraft :showmin'z-Eigure :18 iinilazter :stages; of the- Referring to Figures 1, 2 and 3, an aircraftl is shown resting upon the ground through; a"

landing gear of the bicycle type and including a main strut 2 having the main wheel 2- and the front strut 3 having the nose wheel 3", said aircraft being stabilized against roll by two wing supports 4 and 5. V

When the aircraft is running on the ground during the firstpart of the take-off, as soon as the speed is sufficient to obtain roll and pitch control by means of ailerons 6 and 1. and elevator 8,.main wheel 2'. is moved forward to-the advanced position 2'a shown in Figure 3. This position is selected in the. vertical transverse plane containing the center of. balance of the aircraft Lnamely, the point through which the ground reaction exerted .by .the. ground .on the main wheel must pass in order to keep the balance of other forces-exerted on the aircraft. In thecase illustrated in Fig. 3, the center of balance is.disposed' slightly.forward of the center ofgravity. whenthe craft is moving, although the two coincide when the ship-is at rest. While the craft is moving on the ground, the force of forward motion is exerted along the axis of the craftabove the line along ,whichithe force of drag is exerted by air and ground contact. The force of forward motion and the drag therefore create ,a-,clockwise torque as. viewed in. Fig. 3. This torque. can be overcome by raising the elevator. but this increases air drag, which is undesirable. Consequently, it is better to provide azcounter-torque by advancing the. wheel to the position 2a slightly forward of. the center of gravity; ,i.- .e.-. immediately below the center of balance. Almost immediately thereafter the. nose wheel3' and the two wingsupports 4, and .5 are retracted with the. result of reducing about onehalf the total drag otherwise exerted on the complete landing gear with. the nose wheel and the wing supports in.;projected positions... After the airplane isairborne, the main wheel is retracted,

is important to observe that this reduction of drag takes place in the later part of the take-off run and will be beneficial then as well as in the beginning of the flight, namely, at times where the demand for power from the power plant is at its maximum. Later on, when the aircraft is in flight, the main wheels willv be retracted, and when the aircraft is made ready for the next landing, said main landing wheels will move to their normal back position shown in Figure 4, while the nose wheel is simultaneously projected to its normal landing position.

7 Figures '7 to 11, inclusive, illustrate an aircraft having a landing gear comprising three main struts,.namely, .a pair of struts 2l-22 and a third strut 23, respectively equipped with the three main wheels 2|, 22' and 23', and the front strut 24 having a nose wheel 24'. The paired wheels 2| and 22 are located in the. position of, longitudinal balance of the aircraft as previously set forth in connection with Figures l to 3 The wheel..23 fhas its axis located to" the reanofhwheels 2| and 22, and the nose wheel 24' may have any of the usual positions adopted for aircraft. V When the aircraft of Figures '7 to 11, inclusive, is running on the ground-during thefirstfpai't v of :the take-oif, as soon as the speedis sufficient to .obtainpitch control by means of .elvator'25, the nose wheel 24' is retracted as shown'in Fig--. ure 10. As the aircraft speed increases, the main wheels become partially unloaded 'owingi'to the increasing wind lift up to thepoint where the singlerear wheel 23 may be retracted by appropriate control means provided to that end. Dur ingthe later'stage of the take-off run and'the beginning of flight, there remains only the pair 1 of wheels 2|'22' to cause drag on thelai'rcraft forexample, by. moving the; main strut 2 upward I,

When the aircraft of Figure is running on the .ground during the'firstpart of take-off, as soonas. the speed is sufficient. to obtain longitudinal or pitch control, by .meansof elevator l-4,.the main wheels II and 12" .are moved forward to the advanced positions as indicated at Hluxa'nd .I'Za in Figureb. ..'Ihis forwardlyadvanced position is selected as previously described iil'liCOl'lI'lECtiOl'l with.Figures.1-3.

Thereafter, the nose wheel I3 is retracted with the result of .a'redu'ction of about one-third 'of thetotaldrag exerted on a. complete landing'gear with the nose wheel in operating position. lt

as shown'in Figure llI From". the foregoing, it will be apparent that by following the'same'procedura'the main wheels could be arra nged in a slightlydifleren't manner as shown .in"Figures"12"to' 14' inclusive; For aampiejone main wheel 33' would be mounted the position of .balance'and. the pair of main wheels 3 I"32" vv6u1d be mounted farther to the rearfWith this arrangement, it willbe necessary forthe aircraft."s'll to reach a greater air speed before retracting its main back wheels. than that required with the previous arrangement of Figures f to 11 for retracting the singleback main wheel 23. This is done in order to avoid overload of' .the now "only remaining single main.

' wheel 33:" leftto support the aircraft on the.

ground. This apparent disadvantage may be compensated by the fact that during the later. part of the take-off just one main strut and wheel .cause. air drag as shown in Figures 16 andl'l. 'ii "Figures 18 to 23 inclusive illustrate an aircraft 40 provided with a retractable landing gear comprising four main struts .41, 42, 43 and 44, each equipped with a pair oflanding wheels .4l, T1,

42, 425', 43', 43", 44',.44'.', and with a front strut 45 equipped with a double'n'ose wheel 45 and 45".. Wheels 42', 42" and 43', 43", for convenience called centralmain wheels, are located in;

. 3 the position of longitudinal or pitch balance as previously defined in connection with Figures l to 3. Wh'eels'll', 4i", and'44', 44"are located} farther back than said position of pitchbalance". Similarly to what hasbeen said in connection with the aircraft of Figures '7 to 11, the double nose wheel 45, 45" is retracted as shown in:

Figure '21, when-the air speed 'of the aircraft is" ags'r'nseo sufficient; thereupon wheels ll', ll" mid ll, flare-brought-intotheir 'retracted position-was prising a double nose wheel and four main legsv equipped with a main wheel pair. All main wheels are located in one single row at right angle with the longitudinal axis of the aircraft back ofthe center of pitch balance previously defined; Aircraft B is equipped with a landing gear according to the invention described with respect to Figures 18 to 23. Two pairs of main wheels arelocated just below the center of pitch balance, the other main wheels being mounted in their conventional manner in back of said center of pitch balance.

In the lower halfof Figure 24 it may be assumed that both planes would start from position S. The conventional plane A shown,.-by dotted lines does not become airborne until it reaches the point F. On the other hand, the aircraft B provided with the new landing gear becomes airborne at point F. It may be seen that from position S to F there is no difference;

between the behavior of the two aircrafts. "At position F when the speed of aircraft B is suflicient to insure pitch control, its nose wheels are retracted producing a reduction in the drag as compared to that exerted on aircraft A. L;The result is an increase of acceleration. In position F it is assumed that the speed produces a lift equaling about half the gross weight of aircraft B. Without increasing the wheel load over what it was at standstill, the main back wheels of aircraft B are retracted producing a further reduction in the air drag as compared with that exerted on aircraft A. In rsum, from position F to F aircraft B has only its centermain wheelsin operating position and producing drag on theaircraft. It may thus be plainly seen why aircraft B equipped with the new landing gear operated in the manner specified is capable of taking to air at position F while aircraft A equipped with a landing gear of conventional design takes a longer run, up to position F to take to the air, that is to say, reach a speed relative to the air sufiicient to produce a lift capable of bearing the total gross weight of the aircraft and of producing the minimum lift required for vertical acceleration.

Further, an accurate plot of both speedcurves shows a considerably greater slope of curve VB in position F than curve VA in position It therefore becomes clear that the accumulated difference in speed results in a substantialaltitude of aircraft B at position F where aircraft A is just leaving the ground.

Thecenters of gravity of the airplanes shown respectively in Figs. 1 and '7 are markedflinj each 'c'asei':.- i:

Frgm the foregoing it will be understood that the present invention contemplates the successive retraction of selected portions of the run- 'ning gear while the aircraft is running on the ground during take-6fi'f 'thereby 'inaterially rcducing drag while demand; for powergiis at' sits maximum. Thus, when the craft start toirbecome airborne only a.small partlofmthelanding gear remains to beretra'cte'd andthus remove the last :ves'tige of drag from this source. III/$133M}. i 1'. Foriathe take oifofarriairplane, thefimethod comprising applying "a horizontal propulsive thrust -to' the-airplane tocause -the airplane to move for-ward,-applying"to the 'ground engaging portions of the airplane at the beginning of the ground run vertical supporting forces distributed fore and aft of the center of gravity of the airplane, and modifying the distribution of said supporting forces during the ground run so that, after a given interval, the resultant of the said supporting forces is forward of the center of gravity of the airplane, whereby the moments due to the aerodynamic, thrust, inertia, and ground reaction forces on the airplane will be maintained in substantial equilibrium during the ground run.

2. In the take-off of an airplane having a fore and aft support, the improvement which comprises supporting the airplane on the ground at the beginning of the take-off fore and aft of the center of gravity of the airplane, moving the aft support forward during the take-off until the fore support is just deloaded, retracting the fore support as soon as it is deloaded and while the airplane is still supported aft on the ground and retracting the aft support when the airplane is.

airborne.

3. A take-ofi support system for an airplane comprising a nose strut located on the nose of the airplane and carrying a nose wheel, at least one main strut carrying a first main wheel located on the airplane behind its center of gravity and to the rear of the nose wheel, at least one second main strut carrying a second main wheel located forward of the first main wheel and to the rear of the nose wheel, means for deloading the nose wheel during take-off while the airplane is still on the ground, means for retracting the first main whel after the nose Wheel has been retracted and the airplane is still on the ground, and means for retracting the second main wheel after the airplane is airborne.

4. For the take-off of an airplane having at least three ground engaging portions, one being located at the nose of the airplane and the other two being located fore and aft of the center of gravity of the airplane, ,the method comprising applying a horizontal propulsive thrust to the airplane to cause the airplane to move forward, applying to the ground engaging portions of the airplane at the beginning of the ground run vertical supporting forces distributed fore and aft of the center of gravity of the airplane, and

modifying the distribution of said supporting forces during the ground run by first retracting the ground engaging portion which is located at the nose of the airplane and then retracting the ground engaging portion which is located aft of the center of gravity of the airplane, so that, after a given interval, the resultant of said supporting forces is forward of the center of gravity of the airplane, whereby the moments due to the aerodynamic, thrust, inertia, and ground reaction forces on the airplane will be maintained insubstantial equilibrium during the ground run.

JEAN A. TROENDLE.

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